Date: Mon, 17 Aug 1998 20:54:39 -0700 (PDT) From: Bruce Evans <bde@FreeBSD.ORG> To: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: cvs commit: src/sys/ufs/ufs ufs_bmap.c Message-ID: <199808180354.UAA24421@freefall.freebsd.org>
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bde 1998/08/17 20:54:39 PDT
Modified files:
sys/ufs/ufs ufs_bmap.c
Log:
Quick fix for breakage of read clustering on non-IDE drives. Read
clustering is obsolescent technology so hardly anyone noticed. On
a DORS 32160 SCSI drive with 4 tags, read clustering makes very
little difference even for huge sequential reads. However, on a
ZIP SCSI drive with 0 tags, the minimum overhead per block is about
40 msec, so very large clusters must be used to get anywhere near
the maximum transfer rate. Using clusters consisting of 1 8K block
reduces the transfer rate to about 250K/sec. Under msdosfs, missing
read clustering is normal and a cluster size of 1 512 byte block
reduces the transfer rate to about 25K/sec.
Broken in: rev.1.18
Revision Changes Path
1.22 +2 -2 src/sys/ufs/ufs/ufs_bmap.c
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